God forbid - Phrases/Idioms
The American Heritage® Dictionary of Idioms by Christine Ammer. Copyright © 2003, 1997 by The Christine Ammer 1992 Trust. Published by Houghton Mifflin Harcourt Publishing Company. All rights reserved.
Also, heaven forbid. May God prevent something from happening or being the case. For example, God forbid that they actually encounter a bear, or Heaven forbid that the tornado pulls off the roof. This term, in which heaven also stands for “God,” does not necessarily imply a belief in God's direct intervention but merely expresses a strong wish. [c. 1225] For a synonym, see perish the thought.